--------------------------------------------------
From: "laurent couraud" <l.couraud at gmail.com>
Sent: Wednesday, September 08, 2010 6:08 PM
To: "'Richard Hennessy'" <rich.hennessy at verizon.net>; "'Richard Fateman'" <fateman at cs.berkeley.edu>
Cc: <maxima at math.utexas.edu>
Subject: RE : [Maxima] inf - inf = 0 ??
>
>
>> -----Message d'origine-----
>> De : maxima-bounces at math.utexas.edu [mailto:maxima-bounces at math.utexas.edu] De la part de
>> Richard Hennessy
>> Envoy? : mercredi 8 septembre 2010 23:51
>> ? : Richard Fateman
>> Cc : maxima at math.utexas.edu
>> Objet : Re: [Maxima] inf - inf = 0 ??
>>
>>
>> --------------------------------------------------
>> From: "Richard Fateman" <fateman at cs.berkeley.edu>
>> Sent: Wednesday, September 08, 2010 4:54 PM
>> To: "Richard Hennessy" <rich.hennessy at verizon.net>
>> Cc: <maxima at math.utexas.edu>
>> Subject: Re: [Maxima] inf - inf = 0 ??
>>
>> > On 9/8/2010 12:21 PM, Richard Hennessy wrote:
>> >> I think the user should know better.
>> > There is substantial evidence that this is not always true :)
>> Agreed.
>> I don't think trying to decide if this inf is the same infinity as that one (whatever that
>> means assuming it can even be
>> defined) is the issue.
>>
>> limit(expr1,x,a)-limit(expr2,x,a) is not always an operation on numbers, since it can be
>> shown that infinity is not in
>> the real number system or the complex number system. Perhaps the answer could be put in
>> quotes when it is not a number.
>>
>> Rich
>>
>
> this mean that limit(expr1,x,a)-limit(expr2,x,a) is not equal to limit(expr1-expr2,x,a) ?
> (I'm not mathematician it is why I ask this question)
>
Yes, it does mean that. limit(expr1,x,a)-limit(expr2,x,a) is not always equal to limit(expr1-expr2,x,a);
An example
limit(1/x^2,x,0)-limit(1/x^4,x,0);
inf - inf /* which Maxima converts to 0 */
limit(1/x^2-1/x^4,x,0);
minf
Rich
>>
>> >
>> > If an expression parses", something (meaningful, error, whatever) is computed.
>> > And maybe returned.
>> >
>> > That includes inf-inf.
>> >
>> >
>> >
>>
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>
>